Electrical generators can generate a first AC voltage on the order of some kilovolts and are connected to a transformer that transforms the first voltage to a higher second voltage, which can be in the order of, for example, some 100 kilovolts. In many applications, a circuit breaker, the so-called “generator circuit breaker” (GCB), is arranged between the generator and the transformer.
Up to now, current measurement within a GCB is realized through an inductive current transformer. The primary winding is represented by the current-carrying path of the GCB. The secondary part of the current transformer has an iron core and windings configured according to a desired transmission ratio. The primary current generates magnetic flux in the iron core and thereby a current in the secondary winding.
An exemplary covered current range of the GCB extends from 0 A to 300 kA, for which reason different cores are used to fulfill either protection or measuring purposes. This is because cores designed for high currents do not have sufficient accuracy at lower current ranges. Cores designed for relatively low currents will be saturated by high primary currents, such that the transformer becomes non-linear for high currents.
Known current transformers can be relatively heavy due to their iron core. Therefore, a crane is used for mounting the current transformer to the front side of the GCB.
As a result of customer demands concerning transmission ratio, weight, accuracy class and protection class, a large variety of current transformers exists, which makes standardization impossible.
WO 2005/111633 discloses a concept for the stress-free packaging and orientation of the sensing fiber of a fiber-optic current sensor, such as for the precise measurement of high direct currents at aluminum smelters.